Device for controlling ignition times for internal combustion engine

ABSTRACT

In the normal operation of an engine, the opening of breaker&#39;&#39;s contacts causes a gating diode and therefore an ignition transistor to become conducting to induce an ignition voltage across an ignition coil. In the idling and low speed operations, a monostable multivibrator is enabled to respond to the opening of the breaker&#39;&#39;s contacts to conduct another gating diode after a time interval for which the multivibrator is in its semistable state resulting in the generation of an ignition voltage. In the semistable state a capacitor included in the multivibrator discharges through a transistor serving to maintain the discharge current constant.

Unite States Patent 4/1967 Schneider l23/l 48 Saita Feb. .12, 1974 [54]DEVICE FOR CONTROLLING IGNITION 3,291,108 12/1966 Schneider. 123/148TIMES FOR INTERNAL COMBUSTION FOREIGN PATENTS OR APPLICATIONS ENGINE17,686 9/1966 'Japan 123/148 [75] Inventor; Toshikazu m, Himeji, j a509,801 l2/l952 Belgium l23/l48 [73] Assignee: Mitsubishi DenkiKabushiki Kaisha, Primary Examiner Laurenc Goodridge Tokyo JapanAssistant ExaminerRonald B. Cox [22] Filed: Sept. 27, 1971 Attorney,Agent, or FirmRobert E. Burns; Emmanuel J. Lobato [21] Appl. N0.:183,960

[57] ABSTRACT [30] Foreign Application Priority Data In the normaloperation of an engine, the opening of Sept. 28, 1970 Japan 45-84908breakers contacts Causes 8 gating diode and therefore an ignitiontransistor to become conducting to induce [52] US. Cl. 123/117 R,123/l46.5 A, 123/148 E an ignition voltage across an ignition coil. Inthe idling [51] Int. Cl. F02p 5/04, F02p U00 and low Speed operations, amonostable multivibl'ator [58} Tield of sear cha .Ifi3fiWETI7R, 117 A,is enabled to respond to the opening of the breakers 1211/1465 Acontacts to conduct another gating diode after a time interval for whichthe multivibrator is in its semistable 5 References Ci state resultingin the generation of an ignition voltage.

UNITED STATES PATENTS In the semistable state a capacitor included inthe multivibrator discharges through a transistor serving to C 2maintain the discharge current constant. 31314407 3 Claims, 1 DrawingFigure CIRCUIT CIRCUIT DEVICE FOR CONTROLLING IGNITION TIMES FORINTERNAL COMBUSTION ENGINE BACKGROUND OF THE'INVENTION This inventionrelates to a device for controlling time points at which an internalcombustion engine is to be ignited and more particularly to such adevice suitable for cleaning the exhaust gas from the engine.

It has been already known to control the ignition time point forinternal combustion engines by a single contact breaker having disposedtherein two sets of contacts imparting different ignition times to theassociated engine through the selective use of the two sets .of contactsin accordance with the mode of operation of the engine. In contactbreakers of the type just described, it is required to adjust theopening time point, the contact separation, the angle through which thecontacts are in their closed position etc. for each set of contacts withthe sets of contacts operatively correlated to each other. Therefore thecontact breakers of the double contact type are far more difficult inthe abovementioned adjustment as compared with contact breakersincluding the single set of contacts. Furthermore the double contacttype breakers have operative characteristics that are greatly variableduring service. In addition, the control of the ignition time-point cannot be accomplished by using the existing contact breakers with a singleset of contacts. 7

SUMMARY OF THE INVENTION Accordingly it is an object of the invention toprovide an improved device for controlling the ignition timepoint for aninternal combustion engine comprising a contact breaker having a singleset of contacts, which is substantially free from the disadvantages ofthe prior art practice as above described and suitable for cleaning theexhaust gas from the engine.

The invention accomplishes this object by the provision of a device forcontrolling an ignition time-point for an internal combustion engine,comprising a ignition time detection circuit for producing one signaleach time the engine is to be ignited, a mode detection circuit fordetecting the mode of operation of the engine, and an ignition circuitfor producing an ignition voltage, characterized in that there isprovided a time delay circuit for imparting a predetermined time delayto the signal from the ignition time detection circuit and a selectioncircuit for selecting either the signal from the ignition time detectioncircuit or thetime delayed signal 'from the time delay circuit inaccordance with the mode of operation as detected by the mode detectioncircuit, and the ignition circuit responds to the selected signalapplied thereto to produce the ignition voltage.

The time delay circuit may preferably be formed of a monostablemultivibrator including a capacitor for determining a time interval forwhich the monostable multivibrator is in its semistable state, and acircuit means for charging and discharging the capacitor including meansfor maintaining the charging and discharging currents to and from thecapacitor substantially constant.

BRIEF DESCRIFTION OF THE DRAWING The invention will become more readilyapparent from the following detailed description taken in conjunctionwith the accompanyingdrawing wherein a single FIGURE illustrates acircuit diagram of a device for controlling an ignition time for aninternal combustion engine in accordance with the principles of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, itis seen that an arrangement disclosed herein comprises a source ofdirect current such as a battery connected at the negative terminal toground and an ignition time detection circuit generally designated bythe reference numeral and connected across the source 10. The detectioncircuit 10 includes a set of normally closed contacts 22 disposed in acontact breaker (not shown) and a resistor 24 serially connectedthereto. The contacts 22 are adapted to be opened and closed atpredetermined time intervals in synchronization with the rotationalmovement of the associated internal combustion engine not shown.

The junctionof the contacts 22 and the resistor 24 is connected to botha time delay circuit that will be in detail described hereinafter and agating circuit generally designated by the reference numeral 30. Thegating circuit includes a pair of semiconductor diodes 32 and 34 havingthe respective anode electrodes connected together to the positiveterminal of the source 10 through a resistor 36. A circuit fordeveloping first ignition pulse signals includes the diode 32 having acathode electrode connected to the junction of the contacts 22 and theresistor 24 and the anode electrode also connected to an ignitioncircuit generally designated by the reference numeral 40.

The ignition circuit comprises a pair of grounded emitter transistors 42and 44 shown as being of the n-p-n type. The transistor 42 includes abase electrode connected to the anode electrodes of the gating diodes 32and 34 and a collector electrode connected to the positive terminal ofthe source IO'through a resistor-46 while the transistor 44 includes abase electrode connected to the collector electrode of the transistor 42and a collector electrode connected to the source 10 through a primarywinding of an ignition coil 48 with the collector-to-emitter circuitthereof connected.

across a capacitor 50. The ignition coil 48 includes a secondary windingelectrically coupled to the associated internal combustion engine (notshown) as shown at the arrow.

In the drawing, a block generally designates a mode-of-operationdetection circuit including a set of contacts 62 to detect apredetermined mode of operation of the engine (not shown). For example,the contacts 62 may be operatively coupled to a throttle valve disposedin a suction tube to the engine so that the contacts are in their closedposition in the normal mode of operation of the engine and are in theiropen position in predetermined modes of operation or with the engineoperated in either of the idling and low speed modes. However thethrottle valve and suction tube are not illustrated and are mentionedonly for purposes of illustration.

In the drawing the ignition and mode detection circuits 20 and 60respectively are'shown as being connected to a time delay circuitgenerally designated by the reference numeral 100. The circuit fordeveloping second ignition pulse signals includes time delay circuit 100which comprises a coupling capacitor 102 connected to the junction ofthe breakers contacts 22 and the resistor 24., and a monostablemultivibrator including a pair of grounded emitter transistors 104 and106 shown as being of the n-p-n type, a capacitor 108 and resistors 1and l 12 interconnected in the well known manner as shown. The capacitor108 is connected on each side to the positive terminal of the source 10through a p-n-p transistor 114 or 116 of common base configuration. Morespecifically, the transistor 114 or 116 includes a collector electrodeconnected to each side of the capacitor 108, an emitter electrodeconnected to the source 10 and base electrode connected to groundthrough a resistor 118 or 120 and also to the source 10 through aresistor 122 or 124. The transistor 1 14 or 1 16 forms a part of acircuit for charging or dis charging the capacitor 108 for the purposeas will be apparent later.

The output of the monostable multivibrator as above described or thecollector electrode of the transistor 106 is connected to the positiveterminal of the source 10 through a resistor 126 and also by a resistor128 to a base electrode of a gating transistor 130 including an emitterelectrode grounded and a collector electrode connected the cathodeelectrode of the gating diode 34 and also to a resistor 132 subsequentlyconnected to the positive terminal of the source 10. The base electrodeof the transistor 130 is further connected by a resistor 134 to groundand also to the contacts 62 in the mode detection circuit 60.

The arrangement as above described is operated as follows. Assuming thatthe engine (not shown) is in the normal mode of operation, the modedetection circuit 60 has the contacts 62 put in their closed position asabove described. The closure of the contacts 62 per mits the baseelectrode of the gating transistor 130 to be grounded thereby to put thelatter in its nonconducting state. Also the monostable multivibrator isin its stable state where the transistor 104 is conducting and thetransistor 106 is nonconducting. Thus the potential at the electrode ofthe transistor 130 reversely biases the gating diode 34 to maintain itnonconducting enabling first ignition pulse signals to be developed.

Under these circumstances, the opening of the breakers contacts 22causes a triggering pulse or ignition timing signal to be applied to thetime delay circuit 100 through the coupling capacitor 102 and to thegating diode 32 to be reversely biased. The triggering pulse triggersthe multivibrator from its stable to its semistable state which exhibitsno effect upon the gating circuit 30 because the transistor 130 is inits nonconducting state. The reversely biased diode 32 permits a basecurrent to flow through the transistor 42 in the ignition circuit 40 torender it conducting thus developing a first ignition pulse signal. Thisinterrupts a base current to the transistor 44 to put the latter in itsnonconducting state. As a result, a current flowing through the primarywinding of the ignition coil 48 is interrupted to induce an ignitionvoltage across the secondary winding thereof. As the process justdescribed proceeds instantaneously, the engine is ignited simultaneouslywith the opening of the breakers contacts 22.

Then the breakers contacts 22 will be closed. After the closure of thecontacts 22, the gating diode 42 is forwardly biased to permit a currentflowing through the base circuit of the transistor 42 to flow to groundthrough the diode 32 and the closed contacts 22. This causes theblocking of the transistor 42 to conduct the transistor 44 resulting ina flow of current through the primary winding of the ignition coil 48.The succeeding opening of the breakers contacts 22 repeats the pro cessas above described resulting in the ignition of the engine. Thus it willbe appreciated that each opening of the contacts 22 causes the ignitionof the engine as in the conventional devices.

When the engine is operated in a predetermined mode such as the idlingor low speed mode, the contacts 62 of the mode detection circuit 60 ismaintained in their open position as above described to maintain thetransistor 130 in its conducting state partiaily enabling secondignition pulse signals to be developed. Therefore the gating diode 34 isforwardly biased and conducting. With the breakers contacts 22maintained in their closed position, the gating diode 32 is alsoforwardly biased to maintain the ignition transistor 44 in itsconducting state as above described in conjunction with the normal modeof operation of the engine.

Under these circumstances, the opening of the breakers contacts 22causes the gating diode 32 to be biased in the reverse direction. Thischange in biasing direction has no effect upon the ignition circuit 40because the gating diode 34 is in its conducting state. Simultaneously,a triggering pulse is applied through the capacitor 102 to the baseelectrode of the transistor 104 to trigger the monostable multivibratorfrom its stable state to its semistable state where the transistors 104and 106 become nonconducting and conducting respectively. No conductionof the transistor 106 permits a base current to be applied to thetransistor to render it conducting. Thus the reversely biased diode 34has now been biased in the forward direction to permit the base currentto the transistor 42 to flow to ground therethrough whereby thetransistor 42 continues to be nonconducting.

However, after a predetermined time interval the monostablemultivibrator will be returned back to its stable state. In the stablestate the transistor 106 becomes conducting to put the transistor 130 inits nonconducting state. Thus the gating diode 34 is reversely biasedenabling a second ignition pulse signal to be developed to permit thebase current to be supplied to the transistor 42 to render itconducting. The conduction of the transistor 42 brings the ignitiontransistor 44 into its nonconducting state whereupon the current flowingthrough the primary ignition winding is interrupted to induce anignition voltage across the secondary winding of the ignition coil 48.From the foregoing it will be appreciated that the engine is ignited atthe end of that time interval for which the monostable multivibrator isin its semistable state after the breakers contacts have been opened.

It is well known that the time interval for the semistable state of themonostable multivibrator is substantially equal to a discharging timefor the capacitor 108. On the other hand, in the example illustrated,the monostable multivibrator is in its stable state for a charging timefor the capacitor 108 as determined by a speed of rotation of theengine. In the stable state, the capacitor 108 is charged from thesource 10 through the conducting transistors 114 and 106 while thetransistor 116 is maintained in its nonconducting state because of thepresence of a negative charge on that side of the capacitor 108connectedto the collector electrode of the transistor 116. If T represents a timeinteris charged with a quantity of electricity expressed by (T-z fl, ineach cycle of operation where't is the time interval for which themonostable multivibrator is in its semistable state and I, is amagnitude of a collector current flowing through the transistor 114.

With the monostable multivibrator in its semistable state the capacitor10% is discharged through the conducting transistors 104 and 116 whilethe transistor 1 14 is maintained in its nonconducting state. Thatquantity of electricity discharged from the capacitor 108 is equal tothe quantity of charge (T-t X 1 on the capacitor 108 and expressed by1,, X 1 where I is a magnitude of a collector current flowing throughthe transistor 116. Therefore, the monostable multivibrator has thesemistable time r expressed by This means that the semistable time tvaries in proportion to the time interval T between the triggeringpulses. In other words, the time delay circuit 1011 provides a timedelay varying in proportion to the time interval between the triggeringpulses.

The transistors 114 and 116 are operative to maintain the charging anddischarging currents for the capacitor 108 constant except for thebeginning thereof.

From the foregoing it will be appreciated that the engine is ignitedwith a time delay corresponding to a predetermined fixed angle throughwhich the engines shaft has been rotated after the opening of thebreakers contacts. Therefore, with the engine operated in the idling orlow speed mode, the arrangement disclosed herein is operative in thesimilar manner as does the set of contacts on the receding side disposedin conventional contact breakers including a pair of sets of contacts.

While the invention has been illustrated and described in conjunctionwith a single preferred embodi ment thereof it is to be understood thatnumerous changes and modifications may be resorted to without departingfrom the spirit and scope of the invention. For example, the timeinterval for which the monostable multivibrator is in its semistablestate may be maintained constant by charging and discharging thecapacitor 108 simply through capacitance-resistance networks or the likewithout the constant current circuits including the transistors 114 and116 being used.

In the latter case the time interval for the semistable state of themonostable multivibrator is constant while the ignition time-point onthe receding side is variable in accordance with the speed of rotationof the engine. Also the delay time provided by the time delay circuit101 and therefore the ignition time-point on the receding side may bechanged in accordance with loading on the engine. Further. the contacts62 in the mode detection circuit 60 may be easily replaced by asemiconductor switch. Alternatively the contacts 62 may be transfercontacts. The transfer contacts may be substituted for the gatingcircuit 611 in order to select the ignition time-point in accordancewith the mode of operation of or loading on the engine. in addition, theignition circuit may be of any capacitor discharge type.

In summary, the invention is enabled to control the ignition time forinternal combustion engines with contact breakers including a single setof contacts, as do conventional contact breakers including two sets ofcontacts.

What is claimed is: v

1. A device for controlling an ignition time-point for an internalcombustion engine; comprising: a first ignition generator circuit forgenerating one first ignition signal at each of the ignition time-pointsfor an engine, a second ignition generator circuit responsive to thefirst ignition signals from the first ignition generator circuit fordeveloping variably delayed corresponding second ignition signals andincluding variable time delay means for delaying each second ignitionsignals with respect to the corresponding first ignition signal providedby said first ignition generator circuit for a'time proportioned to theperiod of the period of the corresponding first ignition pulse; amode-of-operation detection circuit operative in accordance with twomodes of operation of the engine to develop mode signals; and anignition circuit responsive to said mode signals for selecting eitherone of the ignition signal sets from said first and second ignitiongenerator circuits thereby to ignite the engine with the selectedignition signals; wherein said time delay means comprises a monostablemultivibrator including a capacitor for determining a time interval forwhich said monostable multivibrator is in its quasi-stable state,circuit means for charging and discharging said capacitor and a constantcurrent circuit for maintaining a substantially constant current flowingthrough said charging -and discharging circuit means.

2. A device for developing ignition pulse signals for controlling theignition timing of an internal combustion engine which develops ignitiontiming signals during use, said device comprising: first circuit meansresponsive to ignition timing signals during use of the device andoperative when enabled for developing first ignition pulse signalsdefining a first timing mode, each first ignition pulse signalcorresponding in time to a corresponding ignition timing signal; secondcircuit means responsive to said ignition timing signals during use andoperative when enabled to coact with said first circuit means fordeveloping variably delayed second ignition pulse signal having aleading edge variably delayed from the leading edge of the correspondingignition timing signal by a time proportional to. theperiod of saidcorresponding ignition timing signal; and means for alternativelyenabling said first circuit means and said second circuit means todevelop said first and second ignition pulse signals. 1

,3. A device according to claim 2, wherein said second circuit meanscomprises means for generating pulse signals each corresponding in timeto a corresponding ignition timing signal and each having a durationproportional to the period of said corresponding ignition timing signal,said means for generating pulse signals comprising a triggerablemonostablemultivibrator having a timing capacitor and means defining aconstant current charge path and a constant current discharge path forsaid timing capacitor, whereby the time for charging said timingcapacitor and the time for discharging said timing capacitor areconstant with respect to each other.

1. A device for controlling an ignition time-point for an internalcombustion engine; comprising: a first ignition generator circuit forgenerating one first ignition signal at each of the ignition time-pointsfor an engine, a second ignition generator circuit responsive to thefirst ignition signals from the first ignition generator circuit fordeveloping variably delayed corresponding second ignition signals andincluding variable time delay means for delaying each second ignitionsignals with respect to the corresponding first ignition signal providedby said first ignition generator circuit for a time proportioned to theperiod of the period of the corresponding first ignition pulse; amode-of-operation detection circuit operative in accordance with twomodes of operation of the engine to develop mode signals; and anignition circuit responsive to said mode signals for selecting eitherone of the ignition signal sets from said first and second ignitiongenerator circuits thereby to ignite the engine with the selectedignition signals; wherein said time delay means comprises a monostablemultivibrator including a capacitor for determining a time interval forwhich said monostable multivibrator is in its quasistable state, circuitmeans for charging and discharging said capacitor and a constant currentcircuit for maintaining a substantially constant current flowing throughsaid charging and discharging circuit means.
 2. A device for developingignition pulse sIgnals for controlling the ignition timing of aninternal combustion engine which develops ignition timing signals duringuse, said device comprising: first circuit means responsive to ignitiontiming signals during use of the device and operative when enabled fordeveloping first ignition pulse signals defining a first timing mode,each first ignition pulse signal corresponding in time to acorresponding ignition timing signal; second circuit means responsive tosaid ignition timing signals during use and operative when enabled tocoact with said first circuit means for developing variably delayedsecond ignition pulse signal having a leading edge variably delayed fromthe leading edge of the corresponding ignition timing signal by a timeproportional to the period of said corresponding ignition timing signal;and means for alternatively enabling said first circuit means and saidsecond circuit means to develop said first and second ignition pulsesignals.
 3. A device according to claim 2, wherein said second circuitmeans comprises means for generating pulse signals each corresponding intime to a corresponding ignition timing signal and each having aduration proportional to the period of said corresponding ignitiontiming signal, said means for generating pulse signals comprising atriggerable monostable multivibrator having a timing capacitor, andmeans defining a constant current charge path and a constant currentdischarge path for said timing capacitor, whereby the time for chargingsaid timing capacitor and the time for discharging said timing capacitorare constant with respect to each other.